An automatic transmission allowing selection between an automatic shift change mode in which automatic shift change is made based on a state of a vehicle (such as a vehicle speed or an accelerator position) and on a shift change map stored in advance and a manual shift change mode in which a shift stage can stepwise be changed by a driver's operation of a switch, a lever or the like has conventionally been known.
For example, Japanese Patent Laying-Open No. 2001-304386 (PTL 1) discloses as such an automatic transmission, a continuously variable transmission for an automobile, with which, even when switching from an automatic shift change mode to a manual shift change mode is made, a proper speed ratio can be maintained without undue fluctuation in an actual speed ratio, and after transition to the manual shift change mode is completed, a speed ratio prepared in advance as a speed ratio for the manual shift change mode is appropriately selected and a shift operation can be made. This continuously variable transmission for an automobile includes drive condition detection means for detecting a drive condition of a vehicle, automatic shift change control means for calculating a target speed ratio for an automatic shift change mode based on the drive condition detected by the drive condition detection means, manual shift change control means for calculating a target speed ratio for a manual shift change mode based on a driver's shift operation, a mode switch for switching a shift change mode, and speed ratio control means for feedback control of an actuator for adjusting a speed ratio such that an actual speed ratio matches with the target speed ratio based on difference between the target speed ratio and the actual speed ratio, characterized by including shift change mode determination means for detecting switching of the shift change mode, drive operation state determination means for determining drive operation contents by the driver that is started up at the time point of detection of switching from the automatic shift change mode to the manual shift change mode by the shift change mode determination means, and target speed ratio calculation means for setting the actual speed ratio immediately before detection of switching from the automatic shift change mode to the manual shift change mode by the shift change mode determination means as an initial value for the target speed ratio in the manual shift change mode and selecting any one of an up-shift side speed ratio and a down-shift side speed ratio in the manual shift change mode closer to the initial value based on the drive operation contents determined by the drive operation state determination means so as to gradually change the target speed ratio from the initial value toward the up-shift side speed ratio or the down-shift side speed ratio.
According to the continuously variable transmission for an automobile disclosed in the publication described above, even in switching from the automatic shift change mode to the manual shift change mode, a proper speed ratio can be maintained without undue fluctuation in the actual speed ratio.